* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -moz-box-sizing: border-box;
    -webkit-box-sizing: border-box;
}
#calc {
    width: 600px;
    margin: 2% auto;
    border: 2px solid #6a6a6a;
    padding: 1%;
}
#calc input {
    display: block;
    width: 100%;
    margin: 2% 0;
    height: 40px;
    padding: 1%;
    font-size: 1.2em;
}
#number-area button{
    width: 183px;
    height: 40px;
    margin: 1% 0;
    display: inline-block;
    font-size: 1.2em;

}
#operations-area {
    margin-top: 2%;
    padding-top: 2%;
    border-top: 1px solid #6a6a6a;
}
#operations-area button{
    width: 107px;
    height: 40px;
    margin: 1% 0;
    display: inline-block;
    font-size: 1.2em;

}
